Objective To investigate the physicochemical and biological properties of a new calcium sulfate-based root canal sealer for deciduous teeth containing calcium sulfate hemihydrate,barium sulfate,chlorhexidine acetate,and polyethylene glycol 400(PEG 400).Methods This study was reviewed and approved by the Ethics Committee.The calcium sulfate hemihydrate and barium sulfate powders with different mass percentages were mixed with liquid PEG 400 at a powder-to-liquid ratio of 3∶1,and chlorhexidine acetate was added to a concentration of 0.2 mg/mL accord-ing to the volume of PEG 400.The above materials were mechanically ground at 250 r/min for 24 h to obtain a calcium sulfate-based root canal sealer for deciduous teeth.The sealer was classified into different groups according to mass percentages of components.The mass percentages of components were optimized by performing time,fluidity,and radi-opacity experiments,and then the pH,mass loss in vitro,and microscopic morphology of the optimal sealer were evaluat-ed.The antimicrobial properties of the sealer were evaluated by a bacterial-material cocultivation method.The cytocom-patibility of the sealer was evaluated by a CCK-8 assay and cytomorphological staining,and its biocompatibility was evaluated by a subcutaneous tissue embedding assay.Results After optimization,mass percentage of calcium sulfate hemihydrate was 80 wt％,and the mass percentage of barium sulfate was 20 wt％.The flowability and radiopacity of the sealer were in accordance with international standards.The pH stabilized between 6-7.On the 7th and 14th days,the pH in the water group was significantly greater than that in the PBS group(P＜0.001),although the pH in both groups gradually increased(P＞0.05).In vitro degradation experiments,the mass loss of the sealer was approximately 15.17％during the preimmersion period,and rate of mass loss decreased after 3 weeks,reaching only approximately 8.33％.X-ray diffraction(XRD)and scanning electron microscopy(SEM)revealed that the main component of the sealer after hydration was calcium sulfate dehydrate.In bacterial growth assays and cytological tests,the sealer showed significant inhibition of the growth of E.faecalis(P＜0.001).After 1 and 4 days of culture,the cell viability in the 1∶10 and 1∶20 sealer extract dilution group was lower than that in the control group(P＜0.05).On the 7th day,the 1∶20 sealer extract dilution had no significant effect on cell proliferation(P＞0.05).Both the sealer group and the control group(Vitapex and zinc oxide eugenol)caused mild inflammatory reactions in tissue sections.Conclusion In this study,a new type of root canal sealer for deciduous teeth was designed based on calcium sulfate,which has good physicochemical properties and strong antibacterial properties and meets biocompatibility requirements.This study provides an idea for the develop-ment of a new type of root canal sealer for deciduous teeth.

Objective The radiation sensitive gene rad 21 of Schizosaccharomyces pombe is involved in the repair of double-stranded breaks in DNA and is essential for mitotic growth. The hHR21sp gene is its human homologue. In an attempt to investigate the role of hHR21sp in DNA repair, we studied the effects of UV and γ-ray irradiation on hHR21sp gene expression in normal human peripheral blood cells, and non-iradiated peripheral and bone marrow cells from Fanconi anemia (FA) patients who have shown DNA repair deficiency.Methods Total steady state RNA was extracted from peripheral blood cells and bone marrow. RNA transcripts were quantified after RT-PCR and Southern blot, phosphoimmage and autoradiogram analysis. The results were compared with control groups. Results hHR21sp expression was significantly increased from 3h to 9h after UV irradiation in peripheral blood cells from normal subjects at doses of 40-80j/m2 (P<0.05). hHR21sp was also up-regulated by γ-ray irradiation at 6h to 9h at dose of 1 to 5Gy (P<0.01), which was more significant than the UV irradiation. In the non-irradiated FA patient group, hHR21sp expression was decreased in bone marrow hematopoietic cells (P<0.05). After activation by PHA and IL-2, there was still a significant depression in expression by the FA patients peripheral blood cells compared with control groups (P<0.05). Conclusion hHR21sp was up-regulated at doses and times irradiated at the range tested in normal peripheral blood cells, and is more affected by γ-ray irradiation than UV irradiation. FA patient bone marrow hematopoietic cells and peripheral blood mononuclear cells showed down-regulation of hHR21sp expression. The results imply that defects in DNA repair via hHR21sp expression may play an important role in the pathogenesis of FA syndrome.